This invention relates to forms for use in casting of concrete walls and more particularly to forms used in the casting of stepped openings in walls.
It is a common practice in the construction of concrete buildings to build concrete houses to cast the walls or wall sections as slabs in horizontal forms. After the concrete has cured, the wall is raised to vertical position, moved into position with other walls of the structure and joined thereto. It is also common practice to cast the wall sections with suitably located door and window openings.
In many instances, the specifications for a wall section will include one or more window or door openings having a stepped configuration to provide a shoulder against which a door or window is to close, and, in many instances, the specifications are such that when the wall is cast in its horizontal form, the shoulder of the opening is facing downwardly. In such case the dimensions of the opening at the upper surface of the poured slab are less than that at the bottom of the slab.
It is a relatively simple matter to design a form having a shape which will give the desired stepped configuration to the opening. However, the construction of such forms represents a significant cost factor. Since the form is larger at the bottom it cannot be removed from the cast slab simply by pulling it out. Removal while the slab is still in place is usually accompanied by partial or complete destruction of the form. As a result, a new form is usually required for each opening to be cast. This increases the cost and increases the chances that the form will not have the precise dimensions desired.
The forms can be removed through the larger side of the opening after the slab has cured and has been raised from the casting pad. However, this necessitates a long delay before any possible reuse of the form.
Window and door openings in the finished wall must also be provided with appropriate hardware so that windows and doors can be hung in the opening. Usually such hardware is installed after the walls are in place, which is a relatively expensive procedure since it requires that holes be drilled into the concrete or that nail guns be used. There have been attempts to secure the hardware to the forms so that the hardware will be cast as the concrete is poured. This has not been too satisfactory since it is difficult and time-consuming to attach the hardware to the form. Also, the hardware must be very carefully positioned on the form so that the cast-in-place hardware will properly mate with the hardware on the doors and windows to be later installed.
It is the principal object of the present invention to provide a form for a stepped opening in a cast concrete wall which can be easily removed after the initial set of concrete and can be promptly reused for forming another opening.
It is a further object of the present invention to provide a form for openings in cast concrete walls which enables hardware to be easily secured to the form and precisely positioned thereon so that such hardware can be cast into the opening as the concrete is poured.